Morphological evolution and management proposals in the Authie Estuary, northern France
Dobroniak, C. (2005). Morphological evolution and management proposals in the Authie Estuary, northern France, in: Herrier, J.-L. et al. (Ed.) Proceedings 'Dunes and Estuaries 2005': International Conference on nature restoration practices in European coastal habitats, Koksijde, Belgium 19-23 September 2005. VLIZ Special Publication, 19: pp. 537-545 In: Herrier, J.-L. et al. (2005). Proceedings 'Dunes and Estuaries 2005': International Conference on nature restoration practices in European coastal habitats, Koksijde, Belgium 19-23 September 2005. VLIZ Special Publication, 19. Vlaams Instituut voor de Zee (VLIZ): Oostende. XIV, 685 pp., more In: VLIZ Special Publication. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISSN 1377-0950, more |  |
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| Abstract | The Authie is a small macrotidal estuary largely infilled by marine sand and affected by flood dominant tides and waves. The shallow estuary mouth exhibits a relatively large intertidal zone of about 2.2km² with saltmarshes and on the south bank a massive sand spit platform. It confines the main Authie channel towards the north bank, threatening the dune barrier and the health and seaside-resort of Berck. The localized erosion and the generalized sedimentation have been focussed for a long time. It poses a number of severe management problems, notably estuarine shoreline protection, and call into question the very survival of the estuary itself. The Regional authority have been aware of these problems and undertook a study on estuary restoration. The first stage consisted in understanding the morphological changes within the estuary. They were deduced from analyses of historical documents, bathymetric charts and from the analysis of successive series of scale-rectified aerial photographs covering the last five decades. The main hydrodynamic processes and transport trends involved in these changes are analysed from observations and measurements of currents and waves. The results show that the width of the estuary mouth has decreased over the centuries. Moreover, the trends observed suggest that morphological changes have been linked to empoldering and the progressive construction of defence structures. The aim of the second stage is to develop predictive scenarios on future evolution of the estuary. Therefore, engineering models have been computed in order to simulate sediment dynamics and several defence schemes and a relocation of the sand platform are proposed. They were also complemented by biological studies on potential impacts of the operation on fauna and flora. The long term objective of the Regional authority is to define the best strategy, fighting the north bank erosion and the generalized sedimentation. But the heightened awareness of the socio-economic and the environmental values of intertidal zone give rise to recommendations on an integrated management of the Authie, notably the interaction between the environment and the shellfish farming ecosystems. |
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